Method of Preparing Phosphorus-Containing Flame Retardants and Their Use in Polymer Compositions

ABSTRACT

A phosphorus-containing flame retardant is produced by reacting at a reaction temperature a mixture including a metal or suitable metal compound and a stoichiometric excess relative to the metal or suitable metal compound of an unsubstituted or alkyl or aryl substituted phosphonic or pyrophosphonic acid, wherein the phosphonic or pyrophosphonic acid is in a molten state at the reaction temperature. The chemical composition of the resulting flame retardant product leads to excellent flame retardancy and exhibits high thermal stability. The presently disclosed flame retardants are useful, for example, in polymer compositions, particularly thermoplastics processed at high temperatures, over a wide range of applications.

This application claims priority benefit to U.S. Provisional ApplicationNo. 62/782,948, filed Dec. 20, 2018, and U.S. Provisional ApplicationNo. 62/923,446, filed Oct. 18, 2019, both of which are incorporatedherein by reference in their entirety.

A highly effective, thermally stable, phosphorus-containing flameretardant is produced by a process comprising reacting a metal orsuitable metal compound with a stoichiometric excess of a phosphonic orpyrophosphonic acid. The chemical composition of the resulting flameretardant, in many embodiments produced as one or predominantly onecompound, leads to excellent flame retardancy and exhibits high thermalstability. The presently disclosed flame retardants are useful, forexample, in polymer compositions, particularly thermoplastics processedat high temperatures, over a wide range of applications.

BACKGROUND

Phosphonic acid salts, i.e., compounds of the formula directly below,are known flame retardants in many polymer compositions:

wherein R is an optionally substituted alkyl, aryl, alkylaryl orarylalkyl group, p is typically a number of from 1 to 4, M is a metal,and y is typically a number of from 1 to 4, so that M_(p) ^((+)y) is ametal cation where (+)y represents the charge formally assigned to thecation.

As disclosed in US 2007/0029532, decomposition of phosphonic acid saltsis known at temperatures encountered during processing of polyesters andpolyamides, damaging the polymers in the process, e.g., temperaturesabove 260 or 270° C.

U.S. Pat. No. 5,053,148 discloses that brittle, heat resistant foams canbe obtained by heating phosphonic acid salts at elevated temperatures.

In Comparative Examples 1 and 2 of U.S. Pat. No. 9,745,449, glass filledpolyamide compositions comprising 10 to 25 wt % of methylphosphonic acidaluminum salt were processed at elevated temperatures. A decrease intorque was observed during compounding, consistent with polymerdegradation, producing a final product material that was friable uponcooling, dusty after grinding, and which could not be molded. Analysisof the compounded material by gel permeation chromatography (GPC) anddifferential scanning calorimetry (DSC) provided additional evidence ofdegradation. The loss of desired polymer properties observed isconsistent with the degradation of polymers suggested in US 2007/0029532and the brittle foam formed in U.S. Pat. No. 5,053,148.

Thus, simple phosphonic acid salts are not suitable for use in manypolymers that are processed at, or subsequently exposed to, hightemperatures, such as 250° C., 260° C., 270° C. or higher, as theyundergo chemical transformation at such temperatures via processes thatharm the polymer. This may happen during compounding, e.g., in anextruder, or while the salt is present in a polymer in a hightemperature application.

On the other hand, U.S. Pat. No. 9,745,449 discloses that heating aphosphonic acid salt at high enough temperatures generally in theabsence of other materials thermally transforms the salt into adifferent, more thermally stable material exhibiting excellent flameretardant activity when incorporated into polymeric substrates. Thethermally transformed materials do not degrade at high temperatures, nordo they cause degradation of a polymer, when processed in polymercompositions at elevated temperatures, e.g., 240° C., 250° C., 260° C.,270° C. or higher, which is an important advantage over previously knownphosphonate salts, which exhibit flame retardant activity but oftendegrade the polymer during processing. The thermally transformedmaterials are described as comprising one or more compounds representedby empirical formula (IV):

wherein R is alkyl or aryl, M is a metal, q is a number of from 1 to 7,e.g., 1, 2 or 3, r is a number from 0 to 5, e.g., 0, 1 or 2, y is anumber of from 1 to 7, e.g., from 1 to 4, and n is 1 or 2, provided that2(q)+r=n(y).

Challenges, however, are encountered with the process and materials ofU.S. Pat. No. 9,745,449, such as the production of product generally inthe form of a solid mass requiring grinding, milling, or other suchphysical processing before use; formation of product mixtures containingwater soluble or thermally unstable compounds; and difficulty incontrolling the phosphorus to metal ratio of the resulting product. Inaddition, the Examples of U.S. Pat. No. 9,745,449 describe producing aphosphorus-containing flame retardant in several steps wherein anintermediate metal salt of a phosphonic acid is produced and the driedsalt is then heated at temperatures over 200° C.

The present disclosure addresses the above-identified challenges, whilealso producing a phosphorus-containing flame retardant without requiringthe production or use of the intermediate salt as described in U.S. Pat.No. 9,745,449.

SUMMARY

In accordance with the present disclosure, a phosphorus-containing flameretardant is produced by a process comprising reacting at a reactiontemperature a mixture comprising a metal or suitable metal compound anda stoichiometric excess relative to the metal or suitable metal compoundof an unsubstituted or alkyl or aryl substituted phosphonic acid,wherein:

-   -   the metal is capable of forming a polycation (i.e., a metal        represented in its corresponding cationic form by the formula        M_(p) ^((+)y) where M is a metal, (+)y represents the charge of        the metal cation, and y is 2 or higher), or the suitable metal        compound is represented by the formula M_(p) ^((+)y)X_(q) where        M is a metal, (+)y represents the charge of the metal cation, y        is 2 or higher, X is an anion, and the values for p and q        provide a charge balanced metal compound;    -   the molar ratio of the unsubstituted or alkyl or aryl        substituted phosphonic acid to the metal or suitable metal        compound in the mixture is higher than 4:1;    -   the reaction temperature is 105° C. or higher; and    -   the unsubstituted or alkyl or aryl substituted phosphonic acid        is in a molten state at the reaction temperature.

Also disclosed is a process of producing a phosphorus-containing flameretardant, comprising reacting at a reaction temperature a mixturecomprising a metal or suitable metal compound and a stoichiometricexcess of an unsubstituted or alkyl or aryl substituted pyrophosphonicacid, wherein:

-   -   the metal is capable of forming a polycation (i.e., a metal        represented in its corresponding cationic form by the formula        M_(p) ^((+)y) as above), or the suitable metal compound is        represented by the formula M_(p) ^((+)y)X_(q) where M is a        metal, (+)y represents the charge of the metal cation, y is 2 or        higher, X is an anion, and the values for p and q provide a        charge balanced metal compound;    -   the molar ratio of the unsubstituted or alkyl or aryl        substituted pyrophosphonic acid to the metal or suitable metal        compound in the mixture is higher than 2:1; and    -   the unsubstituted or alkyl or aryl substituted pyrophosphonic        acid is in a molten state at the reaction temperature.

In the process of the present disclosure, the unsubstituted or alkyl oraryl substituted phosphonic or pyrophosphonic acid, used at astoichiometric excess as described herein, acts as a reagent and solventfor the reaction. Often, the reaction product forms as a slurry as theresulting flame retardant product of the present invention precipitatesfrom the reaction mixture. Excess phosphonic or pyrophosphonic acidremaining after the reaction can be removed along with any possiblebyproducts by filtration and/or washing, e.g., with water. In manyembodiments, a substantially pure flame retardant material is produced,e.g., a flame retardant comprising essentially a single compound withflame retardant activity or essentially a mixture of active compounds.Conversion based on the metal or metal compound is typically high, andthe product can be readily isolated and optionally further purified ifdesired.

The present process overcomes difficulties observed in processes such asfound in U.S. Pat. No. 9,745,449, because, e.g., production of watersoluble or thermally unstable compounds are reduced or avoided, and theflame retardant product, which typically crystallizes as a powder orsmall particles, can be produced directly in a readily processable form,i.e., without requiring or necessitating grinding, granulating, or othersuch physical processing. Further, in many embodiments, the resultingflame retardant material produced according to the present disclosurehas a higher phosphorus to metal ratio than seen with simple metalphosphonates, as further explained herein. High phosphorus to metalratios in the produced flame retardant leads to greater efficiency andcan therefore permit lower loading levels when the flame retardantmaterial is compounded into thermoplastics.

Additional embodiments of the present disclosure include, but are notlimited to, a process for preparing a phosphorus-containing flameretardant, comprising reacting at a reaction temperature a metal orsuitable metal compound with a molar excess of an unsubstituted or alkylor aryl substituted phosphonic acid, wherein the reaction temperature isabout 150° C. or higher, the unsubstituted or alkyl or aryl substitutedphosphonic acid is in a molten state at the reaction temperature, andthe molar ratio of the unsubstituted or alkyl or aryl substitutedphosphonic acid to the metal or suitable metal compound is higher than4:1. In an embodiment, the reaction temperature ranges from about 150°C. to about 300° C., such as from about 150° C. to about 280° C., fromabout 160° C. to about 260° C., or from about 160° C. to about 220° C.In an embodiment, the molar ratio of the unsubstituted or alkyl or arylsubstituted phosphonic acid to the metal or suitable metal compoundranges from about 5:1 to about 30:1. In an embodiment, the suitablemetal compound is a metal oxide, halide, alkoxide, hydroxide,carbon/late, or phosphonate. In an embodiment, the suitable metalcompound is alumina, aluminum trichloride, aluminum trihydroxide, oraluminum isopropoxide.

Other embodiments include, but are not limited to, aphosphorus-containing flame retardant produced according to a processdisclosed herein; a flame retardant polymer composition comprising (i) apolymer and (ii) a phosphorus-containing flame retardant of the presentdisclosure; a process for improving the flame retardancy of a polymer byincorporating therein a flame retardant of the present disclosure; and aprocess for incorporating into a polymer a flame retardant compositioncomprising a flame retardant of the present disclosure.

The preceding summary is not intended to restrict in any way the scopeof the claimed invention. In addition, it is to be understood that boththe foregoing general description and the following detailed descriptionare exemplary and explanatory only and are not restrictive of theinvention, as claimed.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the result of thermogravimetric analysis (TGA) of anexemplary flame retardant material produced according to Example 1 ofthe present disclosure.

DETAILED DESCRIPTION

Unless otherwise specified, the word “a” or “an” in this applicationmeans “one or more than one”.

The term “alkyl” in this application includes “arylalkyl,” unless thecontext dictates otherwise.

The term “aryl” in this application includes “alkylaryl,” unless thecontext dictates otherwise.

The term “phosphonic acid” as used herein refers to unsubstituted oralkyl or aryl substituted phosphonic acid, unless the context dictatesotherwise.

The term “pyrophosphonic acid” as used herein refers to unsubstituted oralkyl or aryl substituted pyrophosphonic acid, unless the contextdictates otherwise.

As used herein, “stoichiometric excess” of the unsubstituted or alkyl oraryl substituted phosphonic or pyrophosphonic acid relative to the metalor suitable metal compound refers to an amount of the phosphonic orpyrophosphonic acid which exceeds that stoichiometrically required forthe reaction between the metal or suitable metal compound and thephosphonic or pyrophosphonic acid. The stoichiometric excess istypically represented by a molar ratio of the phosphonic orpyrophosphonic acid to the metal or suitable metal compound in thereaction mixture, as described herein.

According to one aspect of the present disclosure, a metal or suitablemetal compound and a stoichiometric excess of an unsubstituted or alkylor aryl substituted phosphonic acid are reacted to form aphosphorus-containing flame retardant. The reaction temperature is 105°C. or higher, the phosphonic acid is in a molten state at the reactiontemperature, and the molar ratio of the phosphonic acid to the metal orsuitable metal compound in the reaction mixture is higher than 4:1. Inthe reaction, the metal is oxidized and may be represented in itscorresponding cationic form by the formula M_(p) ^((+)y) where M is ametal, (+)y represents the charge of the metal cation, and y is 2 orhigher. The suitable metal compound may be represented by the formulaM_(p) ^((+)y)X_(q), where M is a metal, (+)y represents the charge ofthe metal cation, y is 2 or higher, X is an anion, and the values for pand q provide a charge balanced metal compound.

In another aspect, a metal or suitable metal compound, as above, and astoichiometric excess of an unsubstituted or alkyl or aryl substitutedpyrophosphonic acid are reacted to form a phosphorus-containing flameretardant. The pyrophosphonic acid is in a molten state at the reactiontemperature, and the molar ratio of the pyrophosphonic acid to the metalor suitable metal compound in the reaction mixture is higher than 2:1.

In many embodiments, the molar ratio of the phosphonic acid to the metalor suitable metal compound in the reaction mixture is 5:1 or higher,such as about 6:1 or higher, about 8:1 or higher, or about 10:1 orhigher. Larger molar excesses of the phosphonic acid to the metal orsuitable metal compound may be used in the reaction mixture, such asabout 12:1 or higher, about 15:1 or higher, about 20:1 or higher, about25:1 or higher, about 30:1 or higher, or any range therebetween. A largemolar excess of the phosphonic acid relative to the metal or suitablemetal compound may be used. For example, the molar ratio may be up toabout 50:1, up to about 100:1, up to about 300:1, up to about 500:1, orany range therebetween. However, as would be understood, processefficiency may suffer at certain large molar excesses, e.g., productprecipitation from the reaction mixture may be hindered. In manyembodiments, the molar ratio ranges from about 8:1, from about 10:1,from about 12:1, or from about 16:1 to about 100:1 or to about 50:1,such as from about 10:1, from about 15:1, or from about 20:1 to about50:1 or to about 40:1.

In many embodiments, the molar ratio of the pyrophosphonic acid to themetal or suitable metal compound in the reaction mixture is 3:1 orhigher, such as about 4:1 or higher, about 6:1 or higher, or about 8:1or higher. Often larger molar excesses of the pyrophosphonic acid to themetal or suitable metal compound are used in the reaction mixture, suchas about 10:1 or higher, about 12:1 or higher, about 15:1 or higher,about 18:1 or higher, about 20:1 or higher, or any range therebetween. Alarge molar excess of the pyrophosphonic acid relative to the metal orsuitable metal compound may be used. For example, the molar ratio may beup to about 30:1, up to about 50:1, up to about 100:1, up to about250:1, or any range therebetween. However, as would be understood,process efficiency may suffer at certain large molar excesses, e.g.,product precipitation from the reaction mixture may be hindered. In manyembodiments, the molar ratio ranges from about 4:1, from about 5:1, fromabout 6:1, or from about 8:1 to about 50:1 or to about 25:1, such asfrom about 5:1, from about 8:1, or from about 10:1 to about 25:1 or toabout 20:1.

The reaction temperature for producing a phosphorus-containing flameretardant according to the present disclosure should be chosen such thatthe phosphonic or pyrophosphonic acid is in a molten state at thereaction temperature. For example, phosphonic and pyrophosphonic acids(e.g., alkyl substituted phosphonic or pyrophosphonic acids) are oftensolid at room temperature (e.g., methyl phosphonic acid melts at about105° C. and ethyl phosphonic acid melts at about 62° C.), and thusheating the phosphonic or pyrophosphonic acid to result in a liquefiedphysical state (i.e., molten state) is generally appropriate to form aconsistent reaction mixture. As one skilled in the art will appreciate,the desired reaction temperature at which the phosphonic orpyrophosphonic acid is in a molten state may vary depending on thechosen reagents and thermodynamic conditions.

The reaction temperature should also be chosen to facilitate theformation of monoanionic and/or dianionic pyrophosphonic acid ligands inthe reaction product. For a phosphonic acid, a reaction temperature of105° C. or higher is used. Without being bound by a particular theory,the reaction temperature is chosen to produce pyrophosphonic acidligands via dehydration reaction(s). In many embodiments, the metal orsuitable metal compound and the phosphonic acid are reacted attemperatures higher than 105° C., such as about 115° C. or higher, about120° C. or higher, about 130° C. or higher, about 140° C. or higher,about 150° C. or higher, about 160° C. or higher, about 170° C. orhigher, about 180° C. or higher, about 200° C. or higher, about 220° C.or higher, about 240° C. or higher, about 260° C. or higher, about 280°C. or higher, or any range therebetween. The reaction temperature may behigher than those described above, such as up to about 350° C., up toabout 400° C., or higher, but it typically does not meet or exceed theboiling temperature of the phosphonic acid. For example, the reactiontemperature may range from about 150° C. to about 300° C., such as fromabout 150° C. to about 280° C., from about 160° C. to about 260° C., orfrom about 160° C. to about 240° C. In many embodiments, the reactiontemperature ranges from about 110° C. to about 350° C., from about 115°C. to about 300° C., from about 125° C. to about 280° C., or from about140° C. to about 260° C. Through the dehydration reaction(s), water isformed, which can potentially lead to the undesirable reverse(hydrolysis) reaction. Thus, in some embodiments, the reaction system isdesigned to facilitate removal, such as the continuous removal, of waterfrom the reaction. For example, the reaction temperature may be chosenabove the boiling temperature of the water to the extent necessary toboil off at least a portion or desired amount (e.g., a majority,substantially all, or all) of the water from the reaction. Additionalmeans, such as a gas purge, vacuum, and/or other known means, may beused to facilitate removal of water from the reaction system.

As dehydration is unnecessary for pyrophosphonic acid, the reactiontemperature for pyrophosphonic acid may be lower than that describedabove for phosphonic acid. Generally, the limiting criterion withrespect to choosing a suitable reaction temperature when employing apyrophosphonic acid is the requirement that the pyrophosphonic acid isin a molten state at the reaction temperature. Often, the metal orsuitable metal compound and the pyrophosphonic acid are reacted at atemperature of 20° C. or higher. In many embodiments, the metal orsuitable metal compound and the pyrophosphonic acid are reacted attemperatures higher than 20° C., such as about 40° C. or higher, about60° C. or higher, about 80° C. or higher, about 100° C. or higher, about140° C. or higher, about 180° C. or higher, about 200° C. or higher, orany range therebetween. The reaction temperature may be higher thanthose described above, such as up to about 300° C., up to about 400° C.,or higher, but it typically does not meet or exceed the boilingtemperature of the pyrophosphonic acid. In many embodiments, thereaction temperature ranges from about 25° C. to about 350° C., fromabout 25° C. to about 280° C., from about 30° C. to about 260° C., fromabout 40° C. to about 260° C., from about 60° C. to about 260° C., fromabout 80° C. to about 240° C., from about 100° C. to about 240° C., fromabout 110° C. to about 240° C., or from about 120° C. to about 240° C.Depending, for example, on the metal compound used to react with thepyrophosphonic acid, water may be generated from the reaction. Asdescribed above, in some embodiments, the reaction system is designed tofacilitate removal, such as the continuous removal, of water from thereaction. For example, the reaction temperature may be chosen above theboiling temperature of the water to the extent necessary to boil off atleast a portion or desired amount (e.g., a majority, substantially all,or all) of the water from the reaction. Additional means, such as a gaspurge, vacuum, and/or other known means, may be used to facilitateremoval of water from the reaction system.

Often, as the reaction progresses, the product forms as a slurry as theresulting flame retardant product precipitates from the product reactionmixture. Thus, the reaction is typically run for a time sufficient toachieve such precipitation. In general, the amount of time required toachieve at least substantial conversion to the flame retardant product,based on the metal or suitable metal compound, will depend on thereaction temperature, with higher temperatures generally resulting inshorter reaction times. In many embodiments, the metal or suitable metalcompound and the phosphonic or pyrophosphonic acid are heated at thereaction temperature for from about 0.1 to about 48 hours, such as fromabout 0.2 to about 36 hours, from about 0.5 to about 30 hours, fromabout 1 hour to about 24 hours, e.g., from about 1 hour to about 12hours, from about 1 hour to about 8 hours, or from about 2 hours toabout 5 hours, although other durations may be used.

The metal or suitable metal compound and the molar excess of thephosphonic or pyrophosphonic acid can be combined in any manner suitableto form the reaction mixture. For example, the phosphonic orpyrophosphonic acid and the metal or metal compound may be mixed (e.g.,stirred) together, such as to form a homogenous reaction mixture. Insome embodiments, the metal or suitable metal compound is added to thephosphonic or pyrophosphonic acid which has been preheated to thereaction temperature. In some embodiments, the phosphonic orpyrophosphonic acid is pre-heated and stirred upon melting, such asunder a nitrogen atmosphere or reduced pressure/vacuum. In still furtherembodiments, the metal or metal compound is added as rapidly as possiblewithout causing a large change in the reaction temperature due to theexothermic nature of the reaction. In some embodiments, the phosphonicor pyrophosphonic acid and the metal or suitable metal compound arecombined without preheating the phosphonic acid, or without sufficientheating to liquefy the phosphonic or pyrophosphonic acid, and thecomponents are subsequently heated to the reaction temperature. The fullamount of metal or suitable metal compound or phosphonic orpyrophosphonic acid can be added to the reaction all at once or inportions. No additional solvents are needed, as the phosphonic orpyrophosphonic acid, used at a molar excess, acts as reagent andsolvent, but additional solvent may be used if desired. In someembodiments, additional solvent is used when employing molar ratios ofphosphonic or pyrophosphonic acid to the metal or suitable metalcompound that are at or near the lower boundary of the molar ratiosdisclosed herein.

In some embodiments, after desired conversion, e.g., full orsubstantially full conversion, to the flame retardant product isachieved, the product reaction mixture is cooled to a temperature aboveor no less than the melting temperature of the excess phosphonic orpyrophosphonic acid to keep the excess phosphonic or pyrophosphonic acidin a liquefied state. The excess phosphonic or pyrophosphonic acid canbe removed by filtration/washing and optionally recovered. The recoveredexcess phosphonic or pyrophosphonic acid may be recycled, e.g., backinto the reactor in which a metal or suitable metal compound reacts withthe phosphonic or pyrophosphonic acid. After conversion to the reactionproduct, a solvent, e.g., water, an alcohol, and/or another suitable(e.g., polar) liquid, may optionally be added to dissolve or otherwisehelp remove the excess phosphonic or pyrophosphonic acid. The flameretardant product is often isolated by filtration, optionally followedby additional work up (e.g., washing, drying, sieving, etc.). Theresulting flame retardant product, which is generally in the form of apowder or small particles, is readily processable, i.e., withoutrequiring or necessitating grinding, milling, or other such physicalprocessing before use. It should be understood that producing the flameretardant material “directly” as a powder or small particles inaccordance with the presently disclosed process permits workup of thereaction product, such as isolating the flame retardant product (e.g.,separating the flame retardant product from excess phosphonic orpyrophosphonic acid or remaining solvent), which may include, e.g.,processing the reaction product by filtering, sieving, washing, drying,and the like. After the reaction, the resulting product reactionmixture, often a slurry, may be cooled to or just above the meltingtemperature of the excess phosphonic acid and the slurry may be combinedwith water. The water/slurry mixture may be agitated as necessary tobreak up any large clumps that might have formed. The solid product maybe isolated by filtration, optionally washed with water and dried, toyield the product in the form of a powder or small particles. In somecases, the product may be sieved to refine the particle size.

The process of the present disclosure yields a flame retardantcomprising one or more metals and one or more mono- and/or bi-dentatepyrophosphonic acid ligands. In some embodiments, compounds thatadditionally comprise phosphonate ligands may be produced, but in allembodiments compounds comprising a pyrophosphonic acid mono-anionicligand and/or a pyrophosphonic acid di-anionic ligand are obtained.

The process may yield mixtures of flame retardant compounds, but in manyembodiments the process yields a flame retardant material as one, orpredominately one, compound, with high conversion based on the metal ormetal compound, such as at least 70%, 80%, 85%, 90%, 95%, 98% or higherconversion, or any range therebetween, as opposed to the mixtures ofcompounds that are obtained with the prior art processes involving heattreatment of metal phosphonate salts. In a general embodiment, in whichphosphonate ligands may be present in the flame retardant product, thereaction proceeds generally as shown:

wherein M is a metal cation and (+)y represents the charge of thecation, e.g., M is a di, tri, tetra, penta-cationic metal; X is ananionic ligand or ligands attached to the metal and the stoichiometry ofM and X (i.e., p and q) provides a charged balanced compound; R is H, analkyl, aryl, alkylaryl or arylalkyl; a, b, c and d represent the ratioof the components to which they correspond relative to one another inthe reaction product, and y, a, b, c and d are values that provide acharged balanced product, with the proviso that y is 2 or more and onlyone of a or c can be 0 (often, c is not zero). In some embodiments, thephosphonic acid ligand above with the coefficient d, when present, maybe present as a dianion. In many embodiments, d is 0.

In a further aspect, a flame retardant product produced according to thepresent disclosure, typically in the form of a powder or smallparticles, comprises a compound or mixture of different compounds ofempirical formula (II)

wherein R is H, an alkyl, aryl, alkylaryl or arylalkyl group, a, b, cand d represent the ratio of the components to which they correspondrelative to one another in the compound, and a is generally a number offrom 0 to 8, e.g., from 0 to 6, from 0 to 4, or from 0 to 2, c isgenerally a number of from 0 to 10, e.g., from 0 to 8, from 0 to 6, from0 to 4 or from 0 to 2, d is generally a number of from 0 to 6, e.g., 0to 4 or 0 to 2, M is a metal, y is a number of from 2 to 5, such as 2, 3or 4, often 2 or 3, and M_(p) ^((+)y) is a metal cation where (+)yrepresents the charge formally assigned to the cation. The values of a,b, c, d and y may vary, but will satisfy the charge-balance equation2(a)+c+d=b(y), and only one of a or c can be 0. In many embodiments, cis not zero. In instances where a di-anionic phosphonic acid ligand ispresent in the compound, the charge balance equation becomes2(a)+c+d+2(d)=b(y). The value for b is limited only in that it mustsatisfy the preceding equations, but in many embodiments b is a numberof from 1 to 4, e.g., 1 or 2. In some embodiments, a is 0, 1, or 2(e.g., 0 or 1), c is 1 or 2, and d is 0, 1, or 2 (e.g., 0 or 1), and theproduct is charged balanced.

In many embodiments, d is 0, as in:

where R, M, y, a, b, and c are as described above and the product chargebalance equation becomes 2(a)+c=b(y).

Often, c in the formulas (II) and (III) above is not zero (e.g., c isfrom 1 to 10, from 1 to 8, from 1 to 6, from 1 to 4, or 1 or 2).

In accordance with the presently disclosed process, it was surprisinglydiscovered in many embodiments, such as when employing di-cationic ortri-cationic metals, that a flame retardant compound is produced where cin the formulas above is not zero and the product has a more favorableratio of phosphorus atoms to metal atoms (i.e., P to M) for providingflame retardancy as compared to phosphorus-containing flame retardantsdescribed in the art. For example, tri-cationic metals (e.g., aluminum)and di-cationic metals (e.g., zinc) are known to form tri-substitutedand di-substituted charge balanced compounds, respectively. As seen inthe art, tris-phosphonate aluminum salts—having a phosphorus to aluminumratio of 3:1—and di-phosphonate zinc salts—having a phosphorus to zincratio of 2:1—are known as flame retardants. However, in accordance withthe pyrophosphonic acid ligand formation of the present disclosure, andparticularly where c in the formulas above is not zero, the ratio ofphosphorus to metal in the flame retardant product is higher. Forexample, as demonstrated in the Examples disclosed herein, whenemploying the process of the present disclosure the ratio of phosphorusto aluminum, or the ratio of phosphorus to iron, in the resulting flameretardant product was 4:1. Such a higher phosphorus to metal ratio leadsto high efficiency and can allow for reduced loadings when compoundedinto thermoplastic polymers.

In certain specific embodiments, y in formula (III) is 2 (i.e., M_(p)^((+)y) is a di-cationic metal, such as described herein), a is 0, b is1, and c is 2. In certain embodiments, the di-cationic metal M is Mg,Ca, or Zn. In other embodiments, y in formula (III) is 3 (i.e., M_(p)^((+)y) is a tri-cationic metal, such as described herein), a is 1, b is1, and c is 1. In certain embodiments, the tri-cationic metal M ischosen from Al, Ga, Sb, Fe, Co, B, and Bi. In certain embodiments, thetri-cationic metal M is Al, Fe, Ga, Sb, or B.

As is common with inorganic coordination compounds, the reaction productin the above described reaction and the compounds of empirical formulas(II) and (III) are idealized such that the reaction product or compoundsmay include coordination polymers, complex salts, salts where certainatomic valences are shared, etc.

For example, in many embodiments, empirical formula (II) or (III)represents a monomer unit (i.e., coordination entity) of a coordinationpolymer, the extended coordination polymer structure thereby forming theflame retardant compound of the present disclosure.

In one example, where M is Al and y is 3, a compound of empiricalformula (III) is produced according to the following empirical formula(IIIa):

As shown herein, the absence of subscripts a, b and c in empiricalformulas indicates that the subscripts are each 1, signifying a 1:1:1ratio of the components (which, in the case of empirical formula (IIIa),a 1:1:1 ratio of di-anionic pyrophosphonic acid ligand, metal atom, andmono-anionic pyrophosphonic acid ligand). In this example, empiricalformula (IIIa) represents a repeating monomer unit (i.e., coordinationentity) of a coordination polymer, the extended coordination polymerstructure thereby forming the flame retardant compound of the presentdisclosure.

Often, a compound of empirical formula (II) or (III), which in manyembodiments is an extended coordination polymer as described herein,makes up all, substantially all, or at least a majority of the flameretardant product, such as at least 75%, 85%, 90%, 95%, 98%, or higher,or any range therebetween, by weight of the flame retardant product.

A compound of empirical formula (II) or (III) (e.g., (IIIa)) may beproduced with high conversion based on the metal or metal compound, suchas at least 70%, 80%, 85%, 90%, 95%, 98% or higher conversion, e.g., atleast 70 to 95% conversion. In certain of these embodiments, M isaluminum (i.e., the reaction product is produced using aluminum or oneor more aluminum compounds, such as those described herein) or iron(i.e., the reaction product is produced using iron or one or more ironcompounds, such as those described herein).

The phosphonic acid used in the present process may be represented byformula (I)

wherein R is H, alkyl, aryl, alkylaryl, or arylalkyl. In manyembodiments, R is H, C₁₋₁₂ alkyl, C₆₋₁₀ aryl, C₇₋₁₈ alkylaryl, or C₇₋₁₈arylalkyl, wherein said alkyl, aryl, alkylaryl, or arylalkyl areunsubstituted or are substituted by halogen, hydroxyl, amino, C₁₋₄alkylamino, di-C₁₋₄ alkylamino, C₁₋₄ alkoxy, carboxy or C₂₋₅alkoxycarbonyl. In some embodiments, said alkyl, aryl, alkylaryl, orarylalkyl are unsubstituted C₁₋₁₂ alkyl, C₆ aryl, C₇₋₁₀ alkylaryl, orC₇₋₁₀ arylalkyl, for example, C₁₋₆ alkyl, phenyl, or C₇₋₉ alkylaryl. Insome embodiments, R is substituted or unsubstituted C₁₋₆ alkyl, C₆ aryl,C₇₋₁₀ alkylaryl, or C₇₋₁₂ arylalkyl, e.g., C₁₋₄ alkyl, C₆ aryl, C₇₋₉alkylaryl, or C₇₋₁₀ arylalkyl. In many embodiments, R is unsubstitutedC₁₋₁₂ alkyl, e.g., C₁₋₆ alkyl. In many embodiments, lower alkylphosphonic acids are used, e.g., methyl-, ethyl-, propyl-, isopropyl-,butyl-, t-butyl- and the like.

R as alkyl may be a straight or branched chain alkyl group having thespecified number of carbons and includes e.g., unbranched alkyls such asmethyl, ethyl, propyl, butyl, pentyl, hexyl heptyl, octyl, nonyl, decyl,undecyl, dodecyl, and branched alkyl such as isopropyl, isobutyl,sec-butyl, t-butyl, ethyl hexyl, t-octyl and the like. For example, R asalkyl may be chosen from methyl, ethyl, propyl, isopropyl, butyl,isobutyl, sec-buty, and t-butyl. In many embodiments, R is methyl,ethyl, propyl or isopropyl, for example methyl or ethyl.

Often, when R is aryl it is phenyl. Examples of R as alkylaryl includephenyl substituted by one or more alkyl groups, for example groupsselected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl,sec-buty, t-butyl, and the like. Examples of R as arylalkyl, include forexample, benzyl, phenethyl, styryl, cumyl, phenpropyl and the like.

In many embodiments, R is chosen from methyl, ethyl, propyl, isopropyl,butyl, phenyl and benzyl.

The pyrophosphonic acid used in the present process may be representedby the formula (Ia):

wherein R is the same as disclosed above for formula (I).

The general reaction scheme with a pyrophosphonic acid and a suitablemetal compound can be represented as:

where R, M, X, p, q, y, a, b and c are as described herein.

The process of the present disclosure may employ more than onephosphonic acid, more than one pyrophosphonic acid, or a combination ofphosphonic and pyrophosphonic acids, so long as the mixture ofphosphonic acids and/or pyrophosphonic acids are in a molten state atthe reaction temperature. In some embodiments, the phosphonic acid orpyrophosphonic acid is generated in situ. For example, phosphonic orpyrophosphonic acid may be prepared, such as by hydrolysis of higheroligomer phosphonic acid and/or cyclic phosphonic acid anhydridestarting materials.

As used herein, “suitable metal compound” and the like refer to acompound of the formula M_(p) ^((+)y)X_(q), where M is a metal capableof forming a polycation, e.g., a metal that forms a cation of 2+, 3+,4+, or 5+, typically 2+, 3+ or 4+, and X is any anion that provides acharged balanced compound with metal M. Suitable examples for X include,but are not limited to, anions that, together with the metal M, formoxides, halides, alkoxides, hydroxides, carbonates, carboxylates, andphosphonates. The values for p and q provide a charge balanced metalcompound, for example, alumina, Al₂O₃. In some embodiments, anunsubstituted metal, M, is used as described herein. Examples ofsuitable metals (M) include, but are not limited to, Mg, Ca, Ba, Zn, Zr,Ge, B, Al, Si, Ti, Cu, Fe, Co, Ga, Bi, Mn, Sn or Sb. In someembodiments, M is chosen from Mg, Ca, Ba, Zn, Zr, Ga, B, Al, Si, Ti, Cu,Fe, Sn or Sb. In some embodiments, M is chosen from Mg, Ca, Ba, Zn, Zr,B, Al, Si, Ti, Fe, Sn or Sb, e.g., M may be Mg, Zn, Ca, Fe or Al.

Suitable metal compounds include, but are not limited to, compoundshaving a metal-oxygen bond, metal-nitrogen bond, metal-halogen bond,metal-hydrogen bond, metal-phosphorus bond, metal sulfur bond, metalboron bond, etc., for example, oxides, halides, alkoxides, hydroxides,carboxylates, carbonates, phosphonates, phosphinates, phosphonites,phosphates, phosphites, nitrates, nitrites, borates, hydrides,sulfonates, sulfates, sulfides, etc., of Mg, Ca, Ba, Zn, Zr, Ge, B, Al,Si, Ti, Cu, Fe, Co, Ga, Bi, Mn, Sn or Sb, for example, oxides,hydroxides, halides, or alkoxides of Mg, Ca, Ba, Zn, Zr, Ga, B, Al, Si,Ti, Cu, Fe, Sn or Sb; such as, oxides, hydroxides, halides, or alkoxidesof Mg, Ca, Ba, Zn, Zr, B, Al, Si, Ti, Fe, Sn or Sb, e.g., oxides,hydroxides, halides, or alkoxides of Mg, Zn, Ca, Fe or Al.

In some embodiments, the metal, M, of the metal or suitable metalcompound is aluminum or iron. In some embodiments, the suitable metalcompound is chosen from halides, oxides, hydroxides, alkoxides,carbonates, carboxylates and phosphonates of aluminum. In someembodiments, the suitable metal compound is chosen from halides, oxides,hydroxides, and alkoxides of aluminum. In some embodiments, the suitablemetal compound is chosen from alumina, aluminum trichloride, aluminumtrihydroxide, aluminum isopropoxide, aluminum carbonate, and aluminumacetate. In other embodiments, the suitable metal compound is chosenfrom halides, oxides, alkoxides, carbonates, and acetates of iron. Insome embodiments, the suitable metal compound is chosen from iron(III)oxide, iron(III) chloride, iron(III) isopropoxide, and iron(III)acetate.

In certain embodiments, R is methyl, ethyl, propyl, isopropyl or butyland M is Al, Fe, Zn or Ca. In further embodiments, X is an oxygen,hydroxy, alkoxy or halogen.

The reaction as described herein may, but need not, be run under reducedpressure or vacuum.

The product reaction mixture formed from the reaction described herein,often presenting as a slurry, may be combined with a liquid (e.g.,water) and agitated as desired to break up any clumps that may haveformed. The solid product may be isolated by filtration, optionallywashed and dried, to yield the product in the form of a powder or smallparticles. In some cases, the product may be sieved to refine theparticle size.

The reaction as described herein may optionally be facilitated with aseeding material. For example, use of a seeding material may reduce thetime to achieve conversion to the flame retardant product and may leadto increased consistency in the product's physical characteristics.Often, the seeding material is added to the reaction mixture upon orafter heating to the reaction temperature. In some embodiments, theseeding material comprises a flame retardant material produced accordingto the process of the present disclosure, such as a flame retardantcompound of empirical formula (II), (III), or (IIIa) as describedherein. The seeding material may be selected or refined to have adesired particle size.

In some embodiments, the suitable metal compound is alumina, and theflame retardant material is produced as follows:

In one example, a phosphonic acid, such as a C₁-C₁₂ alkyl phosphonicacid (e.g., methyl, ethyl, propyl, iso-propyl, butyl or t-butylphosphonic acid) is heated to or above its melting point, 105° C., suchas to 115° C., 125° C., 140° C., 150° C., 160° C., 180° C., 200° C.,220° C., or 240° C. or higher, with stirring (e.g., under nitrogen) uponmelting. An oxide, hydroxide, halide, alkoxide, carbonate or carboxylateof Al, such as alumina, aluminum trichloride, aluminum trihydroxide,aluminum isopropoxide, aluminum carbonate or aluminum acetate, is addedwith stirring at a stoichiometric excess of the phosphonic acid, such asat a molar ratio of phosphonic acid to the metal compound as describedherein, e.g., 5:1 or higher, 10:1 or higher, or 15:1 or higher.Typically, a slurry forms as the reaction proceeds, and the solid flameretardant product may be isolated, such as by filtration, washing, etc.to yield the product in the form of a powder or small particles.Additional workup on the product reaction mixture may be performed priorto isolating the solid product, such as cooling the product reactionmixture above or no less than the melting point of the excess phosphonicacid and combining with a liquid, e.g., water, and optionally agitatedas described above. The solid flame retardant product may be isolated byfiltration, optionally washed with additional solvent and dried, toyield the product in the form of a powder or small particles. The flameretardant product contains phosphorus and aluminum in a 4:1 ratioaccording to the following empirical formula:

In a further example, the example described directly above is performedwith iron or a suitable iron compound, such as halides, oxides,alkoxides, carbonates, or acetates of iron, e.g., iron(III) oxide,iron(III) chloride, iron(III) isopropoxide, or iron(III) acetate. Theflame retardant product contains phosphorus and iron in a 4:1 ratioaccording to the following empirical formula:

Often, the compound of the empirical formulas above (which in manyembodiments is an extended coordination polymer as described herein)makes up all, substantially all, or at least a majority of the flameretardant product, such as at least 75%, 85%, 90%, 95%, 98%, or higher,or any range therebetween, by weight of the flame retardant product.

In some embodiments, the suitable metal compound is a metal phosphonatesalt. The metal in the metal phosphonate salt may be a metal, M, asdescribed herein. The suitable metal compound may be a metal phosphonatesalt of the following formula:

wherein R and M are as described above, p is a number of from 2 to 5,e.g., 2, 3 or 4, and y is a number of from 2 to 5, e.g., 2, 3 or 4, sothat M_(p) ^((+)y) is a metal cation where (+)y represents the chargeformally assigned to the cation. Typically the metal phosphonate salt ischarge balanced (i.e., p=y). The metal phosphonate salt may be preparedaccording to methods known in the art.

In some embodiments, the metal phosphonate salt is prepared from thereaction of an initial metal compound and a phosphonic acid with asolvent (e.g., water) for the phosphonic acid. The initial metalcompound may be a compound according to the suitable metal compounddescribed herein. In some embodiments, the initial metal compound andthe phosphonic acid are reacted at a temperature at or around roomtemperature or at a temperature ranging from about 0 to about 20° C. Theresulting metal phosphonate salt may then be used as the suitable metalcompound according to the inventive process herein.

For example, a phosphonic acid, such as an alkyl phosphonic acid, e.g.,methyl, ethyl, propyl, iso-propyl, butyl or t-butyl phosphonic acid, anda solvent (e.g., water) may be stirred to form a homogeneous solution.Any convenient ratio of water to phosphonic acid may be used, e.g., 10:1to 1:10 by weight, more typically 5:1 to 1:5, and good results have beenachieved using 2:1 to 1:2 mixtures. The solution may be cooled to, e.g.,in the range from about 0 to about 20° C., and an initial metalcompound, such as a metal oxide, halide, alkoxide, or hydroxide, isadded to react with the phosphonic acid. A metal phosphonate salt isformed, which is then used as the suitable metal compound in accordancewith the presently disclosed process. For instance, in a separatereactor, a molar excess of phosphonic acid as described herein (such asat a 5:1 molar ratio of phosphonic acid relative to the metalphosphonate salt) is preheated to a molten state and is reacted with themetal phosphonate salt to form the flame retardant product. Inembodiments involving an aluminum phosphonate salt as the suitable metalcompound, the flame retardant product contains phosphorus and aluminumin a 4:1 ratio of phosphorus to aluminum according to the followingempirical formula:

Often, the compound of the empirical formula (which in many embodimentsis an extended coordination polymer as described herein) makes up all,substantially all, or at least a majority of the flame retardantproduct, such as at least 75%, 85%, 90%, 95%, 98%, or higher, or anyrange therebetween, by weight of the flame retardant product.

The flame retardant of the invention may be used with a variety of otherflame retardants and/or synergists or flame retardant adjuvants as knownin the art. For example, the flame retardant of the invention may beformulated with one or more materials selected from: carbon black,graphite, carbon nanotubes, siloxanes, polysiloxanes; polyphenyleneether (PPE), phosphine oxides and polyphosphine oxides, e.g., benzylicphosphine oxides, poly benzylic phosphine oxides and the like;

melamine, melamine derivatives and melamine condensation products,melamine salts such as, but not limited to, melamine cyanurate, melamineborate, melamine phosphates, melamine metal phosphates, melam, melem,melon, and the like;inorganic compounds including clays, metal salts such as hydroxides,oxides, oxide hydrates, borates, carbonates, sulfates, phosphates,phosphites, hypophosphites, silicates, mixed metal salts, etc., e.g.,talc and other magnesium silicates, calcium silicate, aluminosilicate,aluminosilicate as hollow tubes (DRAGON ITE), calcium carbonate,magnesium carbonate, barium sulfate, calcium sulfate, HALLOYSITE orboron phosphate, calcium molybdate, exfoliated vermiculite, zincstannate, zinc hydroxystannate, zinc sulfide and zinc borate, zincmolybdate (or complexes thereof, e.g., Kemgard 911B), zincmolybdate/magnesium hydroxide complex (e.g., Kemgard MZM), zincmolybdate/magnesium silicate complex (Kemgard 911C), calciummolybdate/zinc complex (e.g., Kemgard 911A), zinc phosphate (orcomplexes thereof, e.g., Kemgard 981), magnesium oxide or hydroxide,aluminum oxide, aluminum oxide hydroxide (Boehmite), aluminumtrihydrate, silica, tin oxide, antimony oxide (III and V) and oxidehydrate, titanium oxide, and zinc oxide or oxide hydrate, zirconiumoxide and/or zirconium hydroxide and the like.

Unless otherwise specified, in the context of the present application,the term “phosphate” when used as a component in a “phosphate salt”,such as in metal phosphate, melamine phosphate, melamine metalphosphate, etc., refers to a phosphate, hydrogen phosphate, dihydrogenphosphate, pyrophosphate, polyphosphate, or a phosphoric acidcondensation products anion or polyanion.

Likewise, unless otherwise specified, in the context of the presentapplication, the term “phosphite” when used as a component in a“phosphite salt”, such as in metal phosphite, etc., refers to aphosphite or hydrogen phosphite.

The flame retardant of the invention may also be formulated with otherflame retardants such as halogenated flame retardants, alkyl or arylphosphine oxide flame retardants, alkyl or aryl phosphate flameretardants, alkyl or aryl phosphonates, alkyl or aryl phosphinates, andsalts of alkyl or aryl phosphinic acid. In some embodiments, the flameretardant comprises a mixture of the flame retardant according to theinstant disclosure and a phosphinic salt of the following formula (e.g.,an aluminum tris(dialkylphosphinate),

R₁ and R₂ each independently may be a group according to R as describedherein, M is a metal as described herein (e.g., Al or Ca), and n is anumber of from 2 to 7, e.g., from 2 to 4, often 2 or 3.

In many embodiments, a flame retardant polymer composition according tothe present disclosure comprises (i) a polymer, (ii) a flame retardantmaterial of the present disclosure, and (iii) one or more additionalflame retardants and/or one or more synergists or flame retardantadjuvants.

For example, in some embodiments the flame retardant polymer compositioncomprises one or more additional flame retardants, e.g., halogenatedflame retardants, phosphine oxide flame retardants, alkyl or arylphosphonates, or salts of alkyl or aryl phosphinates, e.g., an aluminumtris(dialkylphosphinate) such as aluminum tris(diethylphosphinate).

In some embodiments the flame retardant polymer composition comprisesone or more synergists or flame retardant adjuvants, e.g., melamine,melamine derivatives and melamine condensation products (e.g., melam,melem, melon), melamine salts, phosphine oxides and polyphosphineoxides, metal salts such as hydroxides, oxides, oxide hydrates, borates,phosphates, phosphonates, phosphites, silicates and the like, e.g.aluminum hydrogen phosphite, melem or a melamine metal phosphate, e.g.,a melamine metal phosphate wherein the metal comprises aluminum,magnesium or zinc. In particular embodiments the one or more additionalflame retardant, synergist or flame retardant adjuvant comprises analuminum tris(dialkylphosphinate), aluminum hydrogen phosphite,methylene-diphenylphosphine oxide-substituted polyaryl ether,xylylenebis(diphenylphosphine oxide),4,4′-bis(diphenylphosphinylmethyl)-1,1′-biphenyl, ethylenebis-1,2-bis-(9,10-dihydro-9-oxy-10-phosphaphenanthrene-10-oxide)ethane,melem, melam, melon, or dimelamine zinc pyrophosphate.

Certain embodiments provide a halogen free polymer composition. In suchembodiments, halogen containing flame retardants or synergists would beexcluded as much as possible.

The flame retardant material of the present disclosure may be combinedwith an additional flame retardant, synergist or adjuvant in a range of100:1 to 1:100 by weight of the inventive flame retardant to the totalweight of additional flame retardant, synergist and/or adjuvant. In someembodiments, the flame retardant material of the present disclosure ispresent in a range of 10:1 to 1:10 by weight of the inventive flameretardant to the total weight of additional flame retardant, synergistand/or adjuvant, for example, weight ratios ranging from 7:1 to 1:7, 6:1to 1:6, 4:1 to 1:4, 3:1 to 1:3 and 2:1 to 1:2. The inventive flameretardant is often the majority component in such a combination, e.g., a10:1 to 1.2:1 ratio or a 7:1 to 2:1 ratio by weight of the inventiveflame retardant material to the total weight of additional flameretardant, synergist and/or adjuvant, but the inventive material canalso be the minor component of the mixture, e.g., a 1:10 to 1:1.2 ratioor a 1:7 to 1:2 ratio.

The thermally stable flame retardant of the invention can be compoundedinto thermoplastic polymers at high temperatures, such as hightemperature polyamides and polyterephthalate esters, without decomposingor negatively impacting the physical properties of the polymer, and theflame retardant activity is excellent. The flame retardant of theinvention may be used in other polymers, with other synergists and withconventional polymer additives.

The polymer of the flame retardant composition of the present inventionmay be any polymer known in the art, such as polyolefin homopolymers andcopolymers, rubbers, polyesters including polyalkylene terephthalates,epoxy resins, polyurethanes, polysulfones, polyimides, polyphenyleneethers, styrenic polymers and copolymers, polycarbonates, acrylicpolymers, polyamides, polyacetals, and biodegradable polymers. Mixturesof different polymers, such as polyphenylene ether/styrenic resinblends, polyvinyl chloride/acrylonitrile butadiene styrene (ABS) orother impact modified polymers, such as methacrylonitrile andα-methylstyrene containing ABS, and polyester/ABS or polycarbonate/ABSand polyester or polystyrene plus some other impact modifier may also beused. Such polymers are available commercially or made by means wellknown in the art.

The flame retardant of the invention is particularly useful inthermoplastic polymers that are processed and/or used at hightemperatures, for example, styrenic polymers including high impactpolystyrene (HIPS), polyolefins, polyesters, polycarbonates, polyamides,polyurethanes, polyphenylene ethers and the like.

For example, the polymer may be a polyester-series resin, a styrenicresin, a polyamide-series resin, a polycarbonate-series resin, apolyphenylene oxide-series resin, a vinyl-series resin, an olefinicresin, an acrylic resin, epoxy resin, or a polyurethane. The polymer canbe a thermoplastic or a thermoset resin and may be reinforced, e.g.,glass reinforced. In some embodiments, the polymer is a thermoplasticpolyurethane. In some embodiments, the polymer is a thermosetting epoxyresin. More than one polymer resin may be present. In particularembodiments the polymer is an engineering polymer, e.g., a thermoplasticor reinforced thermoplastic polymer, e.g., glass reinforcedthermoplastic polymer, such as an optionally glass filled polyester,epoxy resin or polyamide, for example, a glass-filled polyester such asa glass filled polyalkylene terephthalate, or a glass filled polyamide.

Polyester-series resins include homopolyesters and copolyesters obtainedby, for example, polycondensation of a dicarboxylic acid component and adiol component, and polycondensation of a hydroxycarboxylic acid or alactone component, for example, aromatic saturated polyester-seriesresin, such as polybutylene terephthalate or polyethylene terephthalate.

Polyamide (PA)-series resins include polyamides derived from a diamineand a dicarboxylic acid; polyamides obtained from an aminocarboxylicacid, if necessary in combination with a diamine and/or a dicarboxylicacid; and polyamides derived from a lactam, if necessary in combinationwith a diamine and/or a dicarboxylic acid. The polyamide also includes acopolyamide derived from at least two different kinds of polyamideconstituent components. Examples of polyamide-series resins includealiphatic polyamides such as PA 46, PA 6, PA 66, PA 610, PA 612, PA 11and PA 12, polyamides obtained from an aromatic dicarboxylic acid, e.g.,terephthalic acid and/or isophthalic acid, and an aliphatic diamine,e.g., hexamethylenediamine or nonamethylenediamine, and polyamidesobtained from both aromatic and aliphatic dicarboxylic acids, e.g., bothterephthalic acid and adipic acid, and an aliphatic diamine, e.g.,hexamethylenediamine, and others. These polyamides may be used singly orin combination. In some embodiments, the polymer comprises PA 6. In someembodiments, the polymer comprises PA 66. In some embodiments, thepolymer comprises a polyphthalamide.

Polyamides with melting points of at least 280° C. are used extensivelyfor producing molding compositions which make possible the production ofmolded articles, e.g. for the electrical and electronics industry, withexcellent dimensional stability at high temperatures and with very goodflame-retardant properties. Molding compositions of this type aredemanded for example in the electronics industry for producingcomponents which are mounted on printed circuit boards according to theso-called surface mounting technology, SMT. In this application, thesecomponents must withstand temperatures of up to 270° C. for shortperiods of time without dimensional change.

Such high temperature polyamides include certain polyamides producedfrom alkyl diamines and diacids as polyamide 4,6, however many hightemperature polyamides are aromatic and semi-aromatic polyamides, i.e.,homopolymers, copolymers, terpolymers, or higher polymers that arederived from monomers containing aromatic groups. A single aromatic orsemi-aromatic polyamide may be employed or blends of aromatic and/orsemi-aromatic polyamides are used. It is also possible that thepreceding polyamide and polyamide blends are blended with otherpolymers, including aliphatic polyamides.

Examples of these high temperature aromatic or semi-aromatic polyamidesinclude polyamide 4T, poly(m-xylylene adipamide) (polyamide MXD,6),poly(dodecamethylene terephthalamide) (polyamide 12,T),poly(decamethylene terephthalamide) (polyamide 10,T), poly(nonamethyleneterephthalamide) (polyamide 9,T), hexamethylene adipamide/hexamethyleneterephthalamide copolyamide (polyamide 6,T/6,6), hexamethyleneterephthalamide/2-methylpentamethylene terephthalamide copolyamide(polyamide 6,T/D,T); hexamethylene adipamide/hexamethyleneterephthalamide/hexamethylene isophthalamide copolyamide (polyamide6,6/6,T/6,I); poly(caprolactam-hexamethylene terephthalamide) (polyamide6/6,T); hexamethylene terephthalamide/hexamethylene isophthalamide(6,T/6,I) copolymer; and the like.

Certain embodiments of the invention are thus to compositions comprisinga polyamide that melts at high temperatures, e.g., 280° C. or higher,300° C., or higher, in some embodiments 320° C. or higher, e.g. from 280to 340° C., such as polyamide 4,6 and the aromatic and semi-aromaticpolyamide described above, articles comprising high temperaturepolyamides and the flame retardant material of the invention, methodsfor preparing the compositions and methods for shaping the articles.

As described herein, in many embodiments of the present disclosure, theflame retardant polymer composition comprises (i) a polymer, (ii) theflame retardant of the present disclosure, and (iii) one or moreadditional flame retardants and/or one or more synergists or flameretardant adjuvants. Thus, while the flame retardant (ii) alone exhibitsexcellent activity in polymer systems, it may be used in combinationwith (iii) one or more compounds chosen from other flame retardants,synergists and adjuvants. Exemplary compounds (iii) include halogenatedflame retardants, alkyl or aryl phosphine oxides, alkyl or arylpolyphosphine oxides, alkyl or aryl phosphates, alkyl or arylphosphonates, alkyl or aryl phosphinates, salts of alkyl or arylphosphinic acid, carbon black, graphite, carbon nanotubes, siloxanes,polysiloxanes, polyphenylene ether, melamine, melamine derivatives,melamine condensation products, melamine salts, metal hydroxides, metaloxides, metal oxide hydrates, metal borates, metal carbonates, metalsulfates, metal phosphates, metal phosphonates, metal phosphites, metalhypophosphites, metal silicates, and mixed metal salts. For example, theone or more compounds (iii) may be chosen from aluminumtris(dialkylphosphinate), aluminum hydrogen phosphite, benzylicphosphine oxides, poly benzylic phosphine oxides, melam, melem, melon,melamine phosphates, melamine metal phosphates, melamine cyanurate,melamine borate, talc, clays, calcium silicate, aluminosilicate,aluminosilicate as hollow tubes, calcium carbonate, magnesium carbonate,barium sulfate, calcium sulfate, boron phosphate, calcium molybdate,exfoliated vermiculite, zinc stannate, zinc hydroxystannate, zincsulfide, zinc borate, zinc molybdate, zinc phosphate, magnesium oxide,magnesium hydroxide, aluminum oxide, aluminum oxide hydroxide, aluminumtrihydrate, silica, tin oxide, antimony oxide (III and V), antimony (IIIand V) oxide hydrate, titanium oxide, zinc oxide, zinc oxide hydrate,zirconium oxide, and zirconium hydroxide. For example, the one or morecompounds (iii) may be chosen from aluminum tris(dimethylphosphinate),aluminum tris(diethylphosphinate), aluminum tris(dipropylphosphinate),aluminum tris(dibutylphosphinate), methylene-diphenylphosphineoxide-substituted polyaryl ether, xylylenebis(diphenylphosphine oxide),1,2-bis-(9,10-dihydro-9-oxy-10-phosphaphenanthrene-10-oxide)ethane,4,4′-bis(diphenylphosphinylmethyl)-1,1′-biphenyl, melam, melem, melon,and dimelamine zinc pyrophosphate.

In some embodiments, the flame retardant synergist comprises a materialchosen from melam, melem, melon, melamine cyanurate, melaminepolyphosphate, and melamine-poly(metal phosphate) (e.g.,melamine-poly(zinc phosphate) (Safire 400)). In some embodiments, thesynergist comprises a triazine-based compound, such as a reactionproduct of trichlorotriazine, piperazine and morpholine, e.g.,poly-[2,4-(piperazine-1,4-yl)-6-(morpholine-4-yl)-1,3,5-triazine]/piperazin(MCA® PPM Triazine HF). In some embodiments, the synergist comprises ametal hypophosphite, such as aluminum hypophosphite (e.g., ItalmatchPhoslite® IP-A). In some embodiments, the synergist comprises an organicphosphinate, such as aluminum dialkylphosphinate, e.g., aluminumdiethylphosphinate (Exolit OP).

In some embodiments, the flame retardant polymer composition comprisesone or more compounds chosen from hydrotalcite clays, metal borates,metal oxides, and metal hydroxides, such as metal borates, metal oxides,or metal hydroxides wherein the metal is zinc or calcium.

The concentration of the inventive flame retardant in the polymercomposition is of course dependent on the exact chemical composition ofthe flame retardant, the polymer and other components found in the finalpolymer composition. For example, when used as the sole flame retardingcomponent of a polymer formulation the inventive flame retardant may bepresent in a concentration of from 1 to 50%, e.g., 1 to 30%, by weightof the total weight of the final composition. Typically, when used asthe sole flame retardant there will be at least 2% of the inventivematerial present, for example 3% or more, 5% or more, 10% or more, 15%or more, 20% or more or 25% or more. In many embodiments, the inventiveflame retardant is present in amounts up to 45%, while in otherembodiments, the amount of inventive flame retardant is 40% of thepolymer composition or less, e.g., 35% or less. When used in combinationwith other flame retardants or flame retardant synergists, less of theinventive material may be needed.

Any known compounding techniques may be used to prepare the flameretardant polymer composition of the present disclosure, for example,the flame retardant may be introduced into molten polymer by blending,extrusion, fiber or film formation etc. In some cases the flameretardant is introduced into the polymer at the time of polymerformation or curing, for example, the flame retardant of the inventionmay be added to a polyurethane prepolymer prior to crosslinking or itmay be added to a polyamine or alkyl-polycarboxyl compound prior topolyamide formation or to an epoxy mixture prior to cure.

The flame retardant polymer composition of the invention will oftencontain one or more of the common stabilizers or other additivesfrequently encountered in the art, such as phenolic antioxidants,hindered amine light stabilizers (HALS), the ultraviolet lightabsorbers, phosphites, phosphonites, alkaline metal salts of fattyacids, hydrotalcites, metal oxides, borates, epoxidized soybean oils,hydroxylamines, tertiary amine oxides, lactones, thermal reactionproducts of tertiary amine oxides, thiosynergists, basic co-stabilizers,for example, melamine, melem, etc., polyvinylpyrrolidone, dicyandiamide,triallyl cyanurate, urea derivatives, hydrazine derivatives, amines,polyamides, polyurethanes, hydrotalcites, alkali metal salts andalkaline earth metal salts of higher fatty acids, for example, Castearate, calcium stearoyl lactate, calcium lactate, Zn stearate, Znoctoate, Mg stearate, Na ricinoleate and K palmitate, antimonypyrocatecholate or zinc pyrocatecholate, nucleating agents, clarifyingagents, etc.

Other additives may also be present, for example, plasticizers,lubricants, emulsifiers, pigments, dyes, optical brighteners, otherflame proofing agents, anti-static agents, blowing agents, anti-dripagents, e.g., PTFE, and the like.

Optionally the polymer may include fillers and reinforcing agents, forexample, calcium carbonate, silicates, glass fibers, talc, kaolin, mica,barium sulfate, metal oxides and hydroxides, carbon black and graphite.Such fillers and reinforcing agents may often be present at relativelyhigh concentrations, including formulations where the filler orreinforcement is present in concentrations of over 50 wt % based on theweight of the final composition. More typically, fillers and reinforcingagents are present from about 5 to about 50 wt %, e.g., about 10 toabout 40 wt % or about 15 to about 30 wt % based on the weight of thetotal polymer composition.

In some embodiments, the flame retardant polymer composition of thepresent disclosure is formulated with any one or more materials selectedfrom carbon black, graphite, carbon nanotubes, siloxanes, polysiloxanes,talc, calcium carbonate, magnesium carbonate, barium sulfate, calciumsulfate, calcium silicate, magnesium silicate, aluminosilicate hollowtubes (Dragonite), Halloysite, boron phosphate, calcium molybdate,exfoliated vermiculite, zinc stannate, zinc hydroxystannate, zincsulfide, zinc borate, zinc molybdate (or complexes thereof, e.g.,Kemgard 911B), zinc molybdate/magnesium hydroxide complex (e.g., KemgardMZM), zinc molybdate/magnesium silicate complex (Kemgard 911C), calciummolybdate/zinc complex (e.g., Kemgard 911A), zinc phosphate (orcomplexes thereof, e.g., Kemgard 981) and the like;

hydroxides, oxides, and oxide hydrates of group 2, 4, 12, 13, 14, 15(semi)metals, e.g., magnesium oxide or hydroxide, aluminum oxide,aluminum oxide hydroxide (Boehmite), aluminum trihydrate, silica,silicates, tin oxide, antimony oxide (III and V) and oxide hydrate,titanium oxide, and zinc oxide or oxide hydrate, zirconium oxide and/orzirconium hydroxide and the like; melamine and urea based resins such asmelamine cyanurate, melamine borate, melamine polyphosphate, melaminepyrophosphate, polyphenylene ether (PPE) and the like; and clays,including e.g., hydrotalcite, boehmite, kaolin, mica, montmorillonite,wollastonite, nanoclays or organically modified nanoclays and the like.

In some embodiments, the flame retardant polymer composition of thepresent disclosure is formulated with any one or more materials selectedfrom zinc borate, zinc stannate, polysiloxanes, kaolin, silica,magnesium hydroxide, zinc molybdate complex (e.g., Kemgard 911B), zincmolybdate/magnesium hydroxide complex (e.g., Kemgard MZM), zincmolybdate/magnesium silicate complex (Kemgard 911C), calciummolybdate/zinc complex (e.g., Kemgard 911A), zinc phosphate complex(e.g., Kemgard 981), and melamine-poly(metal phosphate) (e.g.,melamine-poly(zinc phosphate) (Safire 400)).

In some embodiments, in addition to a polymer (such as described herein)and the flame retardant of the present disclosure, the flame retardantpolymer composition comprises melam and any one or more materialsselected from zinc borate, zinc stannate, zinc molybdate complex, zincmolybdate/magnesium hydroxide complex, zinc molybdate/magnesium silicatecomplex, calcium molybdate/zinc complex, zinc phosphate complex, andzinc oxide, optionally with additional additives, such as describedherein.

In some embodiments, in addition to a polymer (such as described herein)and the flame retardant of the present disclosure, the flame retardantpolymer composition comprises melon and any one or more materialsselected from zinc borate, zinc stannate, zinc molybdate complex, zincmolybdate/magnesium hydroxide complex, zinc molybdate/magnesium silicatecomplex, calcium molybdate/zinc complex, zinc phosphate complex, andzinc oxide, optionally with additional additives, such as describedherein.

Further non-limiting disclosure is provided in the Examples that follow.

EXAMPLES Example 1

A three-neck 250 mL flask was charged with 114.6 g methylphosphonicacid, which was then heated. At 105° C. the methylphosphonic acid melts,and vigorous stirring was begun under a N₂ blanket. The methylphosphonicacid was heated to 240° C. and 7.78 g of alumina was added as quickly aspossible without causing a large exotherm. The slurry was cooled untilit was just above the melting point of the excess methyl phosphonicacid, ˜110° C., and then added to 250 mL of H₂O while ensuring that therate of addition did not cause excessive steam formation. The resultingmixture was agitated to break up any large clumps that might haveformed, the product was isolated by filtration, washed with anadditional 750 mL of H₂O, and dried to yield 45.08 g of the product asfine colorless crystals at 87% yield. The product empirical formulaabove represents repeating monomer units (i.e., coordination entities)of a coordination polymer forming the pure crystalline product.Thermogravimetric analysis (TGA) of the product is shown in FIG. 1.

Example 2

A three-neck 250 mL flask was charged with 149.8 g ethylphosphonic acid,which was heated to melting, 62° C. Vigorous stirring was begun under aN₂ blanket, the ethylphosphonic acid was heated to 240° C. and 6.9 g ofalumina was added as quickly as possible without causing a largeexotherm. The slurry was cooled to ˜80° C., and then added to 250 mL ofH₂O while ensuring that the rate of addition did not cause excessivesteam formation. The resulting mixture was agitated to break up anylarge clumps that might have formed, the product was isolated byfiltration, washed with an additional 750 mL of H₂O, and dried to yield49.07 g of the product as fine colorless crystals at 84% yield. Theproduct empirical formula above represents repeating monomer units(i.e., coordination entities) of a coordination polymer forming the purecrystalline product.

Example 3

A resin kettle was charged with 83 g of methylphosphonic acid, which washeated to 120° C. An intermediate material prepared from 50 g. methylphosphonic acid and 35.4 g. aluminum tris(isopropoxide) in the presenceof water was added to the resin kettle as a syrup. The resultingsolution contained a 5:1 molar ratio of methylphosphonic acid:aluminummethylphosphonic acid intermediate, which was heated to 240° C. withmechanical stirring. Stirred continued at 240° C. for about 30 min aftera solid had formed. 500 mL of H₂O was added and the mixture was stirredfor 16 h while a uniform slurry was made. As above, the product wasisolated by filtration, washed with an additional 750 mL of H₂O, anddried to yield 64.3 g of the product as fine colorless crystals at 93%yield. The product empirical formula above represents repeating monomerunits (i.e., coordination entities) of a coordination polymer formingthe pure crystalline product.

Example 4

A three-neck 1 L flask was charged with 1305 g methylphosphonic acid,which was then heated. At 105° C. the methylphosphonic acid melted, andvigorous stirring was begun under vacuum. The methylphosphonic acid washeated to 180° C. and 61 g of alumina was added as quickly as possiblewithout causing a large exotherm or excessive foaming. The slurry wascooled until it was just above the melting point of the excess methylphosphonic acid, ˜110° C., and then added to 1 L of H₂O while ensuringthat the rate of addition did not cause excessive steam formation. Theresulting mixture was agitated to break up any large clumps that mighthave formed, and the product was isolated by filtration, washed with anadditional 1.5 L of H₂O, and dried to yield 408 g of the product as finecolorless crystals at 84% yield. The product empirical formula aboverepresents repeating monomer units (i.e., coordination entities) of acoordination polymer forming the pure crystalline product.

The products from each of Examples 1-4 had a 4:1 P to Al ratio (ICPElemental Analysis).

Example 5

A 1 L reaction vessel was charged with 1412.6 g methylphosphonic acid,which was then heated to 165° C. under nitrogen purge (4 L/min) at 250RPM stirring. 78.2 g of iron oxide was added in portions without causinga large exotherm. The reaction mixture was heated at 165° C. for about24 hours. The product reaction mixture containing an off-white slurryproduct was then cooled to about 130° C. and poured into 1.5 L of waterin a beaker cooled in an ice water bath. The product was isolated byfiltration, washed with an additional 500 mL×3 of water, and dried toyield fine off-white color crystals at 83% yield. The product had a 4:1phosphorus to iron ratio (ICP Elemental Analysis) according to thefollowing empirical formula:

The product empirical formula above represents repeating monomer units(i.e., coordination entities) of a coordination polymer forming the purecrystalline product.

Example 6

Polymer compositions were prepared and evaluated for flame retardantactivity under UL-94 testing. UL-94 V-0 ratings at 0.8 mm thickness weremeasured for glass filled polymer compositions of polyamide 6,6;polyamide 6, polybutylene terephthalate (PBT), and a high temperaturepolyamide containing the flame retardant produced according to Examples1, 3, and 4 above (shown as follows):

TABLE 1 Compositions with UL-94 V-0 rating at 0.8 mm Glass InventiveMelamine Substrate fiber FR Melam cyanurate PA 6,6 30% 12.5% 10% — PA625%   15% — 10% PBT 25%   15% 15% — High temp nylon 25%   18% — —

Additional polymer compositions containing the flame retardant producedaccording to Examples 1, 3 and 4 above combined with various synergistsin glass filled PA 66, PBT and polyphthalamide were prepared andevaluated under UL-94 testing at 0.8 mm thickness. The results areprovided in Table 2 (PA 66), Table 3 (PBT) and Table 4(polyphthalamide). Samples 15, 20 and 22, which did not contain theinventive flame retardant, failed the UL-94 test.

TABLE 2 PA66 Sample Formulation 5 6 7 8 9 10 11 12 13 14 15 PA 66 wt %47.5 46.5 46.5 46.3 45 50 40.3 45.3 45.3 46.3 70 Glass wt % 30 30 30 3030 30 30 30 30 30 30 Inventive FR 12.5 10 10 12.2 14 12 13.7 13.7 13.713.7 — wt % Melam wt % 10 10 10 10 10 — — — — — — Melem wt % — — — — — —16 — — — — Melon wt % — — — — — — — 10 10 — — Melamine — — — — —  8 — —— — — polyphosphate wt % Exolit OP — 3.5 — — — — — — — — — 1230 wt %Exolit OP — — 3.5 — — — — — — — — 1400 wt % PPM Triazine — — — — — — — —— 10 — HF wt % Zinc borate — — — 1.5 — — — 1 — — — wt % Zinc stannate —— — —  1 — — — 1 — — wt % UL 94 @ 1/32″ V-0 V-0 V-0 V-0 V-0 V-0 V-1 V-0V-0 V-1 Fail (0.8 mm)

TABLE 3 PBT Sample Formulation 16 17 18 19 20 PBT wt % 50 50 50 45 75Glass wt % 25 25 25 25 25 Inventive FR wt % 15 16 15 15 — Malam wt % 109 9 15 — Polysiloxane wt % — — 1 — — UL 94 @ 1/32″ V-0 V-0 V-0 V-0 Fail

TABLE 4 Polyphthalamide (High temperature polyamide) Sample Formulation21 22 Polyphthalamide wt % 57 70 Glass wt % 25 30 Inventive FR wt % 18 —UL 94 @ 1/32″ V-0 Fail

Example 7

Polymer compositions containing the flame retardant produced accordingto Example 5 above in PA 66 were prepared and evaluated for flameretardant activity under UL-94 testing at 0.8 mm thickness. The resultsare provided in Table 5. Sample 24, which did not contain the inventiveflame retardant, failed the UL-94 test.

TABLE 5 PA 66 Sample Formulation 23 24 PA 66 wt % 45 70 Glass wt % 30 30Inventive FR wt % 15 — Malam wt % 10 — UL 94 @ 1/32″ V-0 Fail (0.8 mm)

Although particular embodiments of the present invention have beenillustrated and described, it will be apparent to those skilled in theart from consideration of the specification and practice of the presentdisclosure that various modifications and variations can be made withoutdeparting from the scope of the invention, as claimed. Thus, it isintended that the specification and examples be considered as exemplaryonly, with a true scope of the present invention being indicated by thefollowing claims and their equivalents.

1. A process for producing a phosphorus-containing flame retardant,comprising reacting at a reaction temperature a mixture comprising ametal or suitable metal compound and a stoichiometric excess relative tothe metal or suitable metal compound of an unsubstituted or alkyl oraryl substituted phosphonic acid, wherein: the metal is capable offorming a polycation or the suitable metal compound is represented bythe formula M_(p) ^((+)y)X_(q) where M is a metal, (+)y represents thecharge of the metal cation, y is 2 or higher, X is an anion, and thevalues for p and q provide a charge balanced metal compound; the molarratio of the unsubstituted or alkyl or aryl substituted phosphonic acidto the metal or suitable metal compound in the mixture is higher than4:1; the reaction temperature is 105° C. or higher; and theunsubstituted or alkyl or aryl substituted phosphonic acid is in amolten state at the reaction temperature.
 2. A process for producing aphosphorus-containing flame retardant, comprising reacting at a reactiontemperature a mixture comprising a metal or suitable metal compound anda stoichiometric excess relative to the metal or suitable metal compoundof an unsubstituted or alkyl or aryl substituted pyrophosphonic acid,wherein: the metal is capable of forming a polycation or the suitablemetal compound is represented by the formula M_(p) ^((+)y)X_(q) where Mis a metal, (+)y represents the charge of the metal cation, y is 2 orhigher, X is an anion, and the values for p and q provide a chargebalanced metal compound; the molar ratio of the unsubstituted or alkylor aryl substituted pyrophosphonic acid to the metal or suitable metalcompound in the mixture is higher than 2:1; and the unsubstituted oralkyl or aryl substituted pyrophosphonic acid is in a molten state atthe reaction temperature.
 3. The process according to claim 1, whereinthe reaction temperature is about 150° C. or higher.
 4. The processaccording to claim 1, wherein the reaction temperature ranges from about140° C. to about 260° C.
 5. The process according to claim 2, whereinthe reaction temperature is about 40° C. or higher.
 6. The processaccording to claim 2, wherein the reaction temperature ranges from about60° C. to about 260° C.
 7. The process according to claim 1, wherein themolar ratio is 8:1 or higher.
 8. The process according to claim 7,wherein the molar ratio ranges from about 10:1 to about 50:1.
 9. Theprocess according to claim 2, wherein the molar ratio is 4:1 or higher.10. The process according to claim 9, wherein the molar ratio rangesfrom about 5:1 to about 25:1.
 11. The process according to claim 1,wherein the mixture comprises a metal capable of forming a 2+, 3+ or 4+polycation.
 12. The process according to claim 1, wherein the mixturecomprises a suitable metal compound which is represented by the formulaM_(p) ^((+)y)X_(q) where M is a metal, (+)y represents the charge of themetal cation, y is 2, 3 or 4, X is an anion, and the values for p and qprovide a charge balanced metal compound.
 13. The process according toclaim 12, wherein y is
 3. 14. The process according to claim 13, whereinM is chosen from Al, Ga, Sb, Fe, Co, B, and Bi.
 15. The processaccording to claim 14, wherein M is Al or Fe.
 16. The process accordingto claim 1, wherein the reaction mixture comprises the suitable metalcompound, and the suitable metal compound is chosen from a metal oxide,halide, alkoxide, hydroxide, carbonate, carboxylate, or phosphonate. 17.The process according to claim 16, wherein M in the formula M_(p)^((+)y)X_(q) is Al.
 18. The process according to claim 17, wherein thesuitable metal compound is chosen from alumina, aluminum trichloride,aluminum trihydroxide, aluminum isopropoxide, aluminum carbonate,aluminum acetate, iron(III) oxide, iron(III) chloride, iron(III)isopropoxide, and iron(III) acetate.
 19. The process according to claim1, wherein the unsubstituted or alkyl or aryl substituted phosphonicacid is represented by formula (I)

wherein R is H, C₁₋₁₂ alkyl, C₆₋₁₀ aryl, C₇₋₁₈ alkylaryl, or C₇₋₁₈arylalkyl, wherein the alkyl, aryl, alkylaryl, or arylalkyl areunsubstituted or are substituted by halogen, hydroxyl, amino, C₁₋₄alkylamino, di-C₁₋₄ alkylamino, C₁₋₄ alkoxy, carboxy or C₂₋₅alkoxycarbonyl.
 20. The process according to claim 2, wherein theunsubstituted or alkyl or aryl substituted pyrophosphonic acid isrepresented by formula (Ia)

wherein R is H, C₁₋₁₂ alkyl, C₆₋₁₀ aryl, C₇₋₁₈ alkylaryl, or C₇₋₁₈arylalkyl, wherein the alkyl, aryl, alkylaryl, or arylalkyl areunsubstituted or are substituted by halogen, hydroxyl, amino, C₁₋₄alkylamino, di-C₁₋₄ alkylamino, C₁₋₄ alkoxy, carboxy or C₂₋₅alkoxycarbonyl.
 21. The process according to claim 19, wherein R isunsubstituted C₁₋₁₂ alkyl, C₆ aryl, C₇₋₁₀ alkylaryl, or C₇₋₁₀ arylalkyl.22. The process according to claim 21, wherein R is unsubstituted C₁₋₆alkyl.
 23. The process according to claim 19, wherein R is methyl,ethyl, propyl, isopropyl, butyl, or t-butyl.
 24. A phosphorus-containingflame retardant produced according to the process of claim 1 directly inthe form of a powder or small particles.
 25. The phosphorus-containingflame retardant according to claim 24, wherein y is 2 or
 3. 26-54.(canceled)
 55. A flame retardant material comprising a compound ofempirical formula (III)

wherein R is H, an alkyl, aryl, alkylaryl, or arylalkyl group; M is ametal and y is 2 or 3, such that MM_(p) ^((+)y) is a metal cation where(+)y represents the charge formally assigned to the cation; a, b, and crepresent the ratio of the components to which they correspond relativeto one another in the compound, and satisfy the charge-balance equation2(a)+c=b(y); and c is not zero; and wherein the compound of empiricalformula (III) makes up at least a majority by weight of the flameretardant material.
 56. The flame retardant material according to claim55, wherein a is 0, 1 or 2, b is from 1 to 4 and c is 1 or
 2. 57. Theflame retardant material according to claim 55, wherein y is 3, a is 1,b is 1 and c is
 1. 58. The flame retardant material according to claim57, wherein M is chosen from Al, Ga, Sb, Fe, Co, B, and Bi.
 59. Theflame retardant material according to claim 58, wherein M is Al or Fe.60. The flame retardant material according to claim 55, wherein R is H,C₁₋₁₂ alkyl, C₆₋₁₀ aryl, C₇₋₁₈ alkylaryl, or C₇₋₁₈ arylalkyl, whereinthe alkyl, aryl, alkylaryl, or arylalkyl are unsubstituted or aresubstituted by halogen, hydroxyl, amino, C₁₋₄ alkylamino, di-C₁₋₄alkylamino, C₁₋₄ alkoxy, carboxy or C₂₋₆ alkoxycarbonyl.
 61. The flameretardant material according to claim 60, wherein R is unsubstitutedC₁₋₁₂ alkyl, C₆ aryl, C₇₋₁₀ alkylaryl, or C₇₋₁₀ arylalkyl.
 62. The flameretardant material according to claim 60, wherein R is unsubstitutedC₁₋₆ alkyl.
 63. The flame retardant material according to claim 62,wherein R is chosen from methyl, ethyl, propyl, isopropyl, butyl andt-butyl.
 64. The flame retardant material according to claim 55, whereinthe compound of empirical formula (III) makes up at least 75% by weightof the flame retardant material.
 65. The flame retardant materialaccording to claim 55, wherein the compound of empirical formula (III)is a compound of empirical formula (IIIa)

wherein R is H or alkyl.
 66. The flame retardant material according toclaim 65, wherein R is unsubstituted C₁₋₆ alkyl.
 67. The flame retardantmaterial according to claim 65, wherein R is methyl or ethyl.
 68. Theflame retardant material according to claim 65, wherein the compound ofempirical formula (IIIa) makes up at least 75% by weight of the flameretardant material.
 69. The flame retardant material according to claim65, wherein the compound of empirical formula (IIIa) makes up at least90% by weight of the flame retardant material.
 70. A flame retardantpolymer composition comprising (i) a polymer and (ii) the flameretardant material according to claim
 55. 71. The flame retardantpolymer composition according to claim 70, wherein the polymer comprisesone or more of a polyolefin homopolymer or copolymer, rubber, polyester,epoxy resin, polyurethane, polysulfone, polyimide, polyphenylene ether,styrenic polymer or copolymer, polycarbonate, acrylic polymer,polyamide, or polyacetal.
 72. The flame retardant polymer compositionaccording to claim 70, wherein the polymer comprises one or more of astyrenic polymer or copolymer, polyolefin homopolymer or copolymer,polyester, polycarbonate, acrylic polymer, epoxy resin, polyamide, orpolyurethane.
 73. The flame retardant polymer composition according toclaim 70, wherein the polymer comprises a polyalkylene terephthalate,high impact polystyrene (HIPS), epoxy resin, or polyamide.
 74. The flameretardant polymer composition according to claim 73, wherein the polymercomprises a glass filled polyalkylene terephthalate, glass reinforcedepoxy resin, or a glass filled polyamide.
 75. The flame retardantpolymer composition according to claim 73, wherein the polymer comprisesa polyphthalamide.
 76. The flame retardant polymer composition accordingto claim 73, wherein the polymer comprises polyamide 46, polyamide 6,polyamide 66, polyamide 4T, or polyamide 9T.
 77. The flame retardantpolymer composition according to claim 73, wherein the polymer comprisespolyamide MXD,6, polyamide 12,T, polyamide 10,T, polyamide 6,T/6,6,polyamide 6,T/D,T, polyamide 6,6/6,T/6,l, polyamide 6/6,T, or polyamide6,T/6,l.
 78. The flame retardant polymer composition according to claim70, wherein the polymer comprises a polyphenylene ether/styrenic resinblend, acrylonitrile butadiene styrene (ABS), polyvinyl chloride/ABSblend, methacrylonitrile/ABS blend, α-methylstyrene containing ABS,polyester/ABS, polycarbonate/ABS, impact modified polyester, or impactmodified polystyrene.
 79. The flame retardant polymer compositionaccording to claim 70, further comprising (iii) one or more compoundschosen from additional flame retardants, synergists, and flame retardantadjuvants.
 80. The flame retardant polymer composition according toclaim 79, wherein the one or more compounds are chosen from halogenatedflame retardants, alkyl or aryl phosphine oxides, alkyl or arylpolyphosphine oxides, alkyl or aryl phosphates, alkyl or arylphosphonates, alkyl or aryl phosphinates, salts of alkyl or arylphosphinic acid, carbon black, graphite, carbon nanotubes, siloxanes,polysiloxanes, polyphenylene ether, melamine, melamine derivatives,melamine condensation products, melamine salts, metal hydroxides, metaloxides, metal oxide hydrates, metal borates, metal carbonates, metalsulfates, metal phosphates, metal phosphonates, metal phosphites, metalhypophosphites, metal silicates, and mixed metal salts.
 81. The flameretardant polymer composition according to claim 80, wherein the one ormore compounds are chosen from aluminum tris(dialkylphosphinate),aluminum hydrogen phosphite, benzylic phosphine oxides, poly benzylicphosphine oxides, melam, melem, melon, melamine phosphates, melaminemetal phosphates, melamine cyanurate, melamine borate, talc, clays,calcium silicate, aluminosilicate, aluminosilicate as hollow tubes,calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate,boron phosphate, calcium molybdate, exfoliated vermiculite, zincstannate, zinc hydroxystannate, zinc sulfide, zinc borate, zincmolybdate, zinc phosphate, magnesium oxide, magnesium hydroxide,aluminum oxide, aluminum oxide hydroxide, aluminum trihydrate, silica,tin oxide, antimony oxide (Ill and V), antimony (III and V) oxidehydrate, titanium oxide, zinc oxide, zinc oxide hydrate, zirconiumoxide, and zirconium hydroxide.
 82. The flame retardant polymercomposition according to claim 81, wherein the one or more compounds arechosen from aluminum tris(dimethylphosphinate), aluminumtris(diethylphosphinate), aluminum tris(dipropylphosphinate), aluminumtris(dibutylphosphinate), methylene-di phenyl phosphineoxide-substituted polyaryl ether, xylylenebis(diphenylphosphine oxide),1,2-bis-(9,10-dihydro-9-oxy-10-phosphaphenanthrene-10-oxide)ethane,4,4′-bis(diphenylphosphinylmethyl)-1,1′-biphenyl, melam, melem, melon,and dimelamine zinc pyrophosphate.
 83. The flame retardant polymercomposition according to claim 70, further comprising one or morecompounds chosen from hydrotalcite clays, metal borates, metal oxides,and metal hydroxides.
 84. The flame retardant polymer compositionaccording to claim 83, wherein the metal of the metal borates, metaloxides, and metal hydroxides is zinc or calcium.
 85. The flame retardantpolymer composition according to claim 79, wherein the one or morecompounds are chosen from melam, melem, melon, melamine cyanurate,melamine polyphosphate, melamine poly(metal phosphate),poly-[2,4-(piperazine-1,4-yl)-6-(morpholine-4-yl)-1,3,5-triazine]/piperazin,aluminum hypophosphite, and aluminum dialkylphosphinate.
 86. The flameretardant polymer composition according to claim 79, wherein the one ormore compounds are chosen from zinc borate, zinc stannate,polysiloxanes, kaolin, silica, magnesium hydroxide, zinc molybdatecomplex, zinc molybdate/magnesium hydroxide complex, zincmolybdate/magnesium silicate complex, calcium molybdate/zinc complex,zinc phosphate complex, and melamine-poly(zinc phosphate).
 87. The flameretardant polymer composition according to claim 79, wherein the one ormore compounds comprise melam and any one or more materials selectedfrom zinc borate, zinc stannate, zinc molybdate complex, zincmolybdate/magnesium hydroxide complex, zinc molybdate/magnesium silicatecomplex, calcium molybdate/zinc complex, zinc phosphate complex, andzinc oxide.
 88. The flame retardant polymer composition according toclaim 79, wherein the one or more compounds comprise melon and any oneor more materials selected from zinc borate, zinc stannate, zincmolybdate complex, zinc molybdate/magnesium hydroxide complex, zincmolybdate/magnesium silicate complex, calcium molybdate/zinc complex,zinc phosphate complex, and zinc oxide.
 89. A flame retardant polymercomposition comprising (i) a polymer and (ii) the flame retardantmaterial according to claim
 65. 90. A process for increasing the flameresistance of a polymer, comprising incorporating the flame retardantmaterial according to claim 55 into a polymer resin, optionally with oneor more additional flame retardant, synergist or flame retardantadjuvant.
 91. A process for increasing the flame resistance of apolymer, comprising incorporating the flame retardant material accordingto claim 65 into a polymer resin, optionally with one or more additionalflame retardant, synergist or flame retardant adjuvant.